There are about 6 billion of us at the moment with an estimated 90 million more born each year.
That is a lot of people in a fixed amount of space!
Overpopulation occurs when there are more people than the land can sustain.
A lower death rate is a good thing. Modern medicine and farming techniques have allowed us to reduce deaths through starvation and disease.
However the birth rate has increased alarmingly. It has resulted in population rises that are out of control, many of these are in so-called 'under-developed' countries.
As the population of a country rises so there more people to feed and support.
As the poorer, under-developed countries become more industrialised they use more of their limited resources for their growing populations. They want to provide all the essentials such as health care and education.
These growing economies demand more energy from fossil fuels, adding to the pollution problems.
Deforestation is increased to provide building land, timber and farmland. This includes the essential rainforests. Areas the size of Wales are lost each year.
Mining and other extraction techniques lead to reduced mineral reserves.
But these effects include us too. Our demand for materials and energy is much greater than under-developed countries. They just want what we want. They have that right, don't they?
We want new things and to run all our equipment - including computers!
Overpopulation is a global problem - but it is also personal.
At this present rate there will be many billions of people trying to live in smaller and smaller areas, fighting for fewer and fewer resources.
Not a great vision of the future is it!
We must do something. But what?
Encouragingly, a lot of time has been spent over recent years into examining what might be done. Some countries have introduced strict birth control laws. China has even made it illegal to have more than one child!
Education, including about contraception and birth control is another key measure. This has been shown to help to reduce the birth rate in a population.
However, this can be an expensive and difficult measure to introduce.